Zombie Apocalypse!

Hi! This Is My First Game In GameMaker And I'm Still Learning. Please Give Me Feedback On What To Add/Remove/Improve On. My Original Game Idea Was To Make A Zombie Shooter And I Think I Completed My Goal. A Couple Challenges That I Ran Into Were Making Different Weapons Do Different Things, And Making It So The Zombies Would Collide And Not 'Fuse Together'. Most Of My Playtests Were Started With The Infamous Error Screen, But Everything Worked Out In The End. The Feedback Of Playtesting Helped Extraordinarily To The Development. Because Of The Testing, I Learned A l]Lot About Object Parents And Scripting. In The Future, I Think I Could Add A Multitude Of Levels, Extended Maps, And Enemies With Different Perks(Speed, Regen, ect). Thanks For Reading, And Enjoy The Game! (Press Esc To Quit)